suos amores This could mean "girl friend" or it could mean his "main squeeze."

illepidum... invenustum are plays on lepos and venus, words that belong to Catullus' in-crowd. In a sense he is saying that the scortillum is "one of us" -- or, rather, NOT one of us.

Lines 5-8
Bithynia is a Roman province on the Black Sea.

profuisset aere Presumably this is a reference to ripping off the locals. It would seem that Catullus' boss was upright and saw to it that the province was well governed.

Lines 9-13
respondi id quod erat trans. " I told it like it was."

caput unctius referret trans. "come back with a greased palm."; in ancient Rome, they greased heads. In any case, the phrase refers to kickbacks.

praetor Catullus' praetor was C. Memmius. He was governor of Bithynia in 57-6 BCE. We know him from other sources as the son-in-law of Sulla and the man to whom Lucretius dedicates his epic poem De rerum natura . As to his being difficult, we have only Catullus' word. The Roman aristocracy pursued the cursus honorum, a series of offices held in sequence up to the highest office. The first office was quaestor; he went along with a governor to a province and served as the financial officer. After serving as quaestor, a man could become a member of the Senate. The next office was the aedileship; the aedile was in charge of religious festivals or building projects. The praetorship followed, a judicial office. After serving as praetor, one could be sent to govern a province. The highest magistrate was the consul; two were elected each year to govern the state.

faceret pili is an idiom meaning "to give a damn for."

Lines 14-23
quod illic natum dicitur esse refers either to the practice of using a litter or to the fact that Bithynia was famous for eight-man litter bearers (cf. Cicero,Verrines 5.28).

provincia quod mala incidisset is a reference to the Roman practice of assigning provinces to governors by lot. Thus, a province would literally "fall out" for a governor and his cohort.

grabatus more a cot than a bed.

Lines 24-30
cinaedus This is a common term of abuse in Catullus. It refers to a man who likes to be sodomized. The way that Romans seemed to have conceptualized sexuality, especially for a man, was that there was great shame in having one's body penetrated and honor in penetrating the body of another. So, to be someone who enjoys being penetrated was to be as base as one can be.

ad Serapim Serapis, an Egyptian deity, was the consort of the goddess Isis. His cult had become popular in Rome and some attempt was made to suppress it in the middle of the 1st century BCE. It is significant, if for no other reason than that it is very un-Roman, that the scortillum wants to go there.

fugit me ratio idiomatic for "what was I thinking?" or "I misspoke" or "what I meant to say."

Gaius Cinna is a poet-friend of Catullus (Carm.95). He may have been in Bithynia with Catullus or the poet may just be grabbing a name out of the air.

Lines 31-34
quid ad me trans. "what does it matter to me?"

insulsa like lepos and venus mentioned above, salsus is used to describe the in-people of Catullus' group. Thus, the scortillum, who seemed at the outset to be one of the gang, is clearly not. She lacks taste, the primary requirement to be part of Catullus' group.